1. Field of the Invention
This invention pertains to processes for gasifying hydrocarbon feedstocks to form an effluent consisting essentially of methane and an aromatic fraction which is substantially benzene, and to the production of synthetic natural gas (methane) by the gasification of hydrocarbon feedstocks. Hydrocarbon feedstocks are vaporized in the presence of hydrogen and then, with an excess of hydrogen, are reacted at high temperature to produce an effluent gas containing essentially methane, aromatics, acid gases such as hydrogen sulfide and excess hydrogen. In one aspect of the invention, the effluent from the gasification step is then further processed by condensing and/or absorbing out the aromatic fraction, removing the acid gases and finally, separating the hydrogen from the methane to produce a synthetic natural gas (SNG) having a heating value of approximately 1,000 BTU/SCF. The resulting synthetic natural gas can be discharged into a storage receptacle or put into a pipeline for use by residential communities or industrial concerns. The aromatics removed from the gasifier effluent are revaporized and recycled to the gasifier for reaction to extinction. The acid gases containing mainly hydrogen sulfide are reacted to produce elemental sulfur.
The gasifier effluent is suitable as a plant fuel or feedstream for further processing into a hydrogen-carbon monoxide synthesis gas or hydrogen gas.
2. Prior Art
Gasification of hydrocarbon feedstocks, mainly crude oil and crude oil fractions, to produce a synthetic pipeline gas either rich in hydrogen or rich in methane is shown by many processes in the prior art. These processes are extensively discussed in the specification of U.S. Pat. No. 3,870,481 which is owned by the assignee of this application. The specification of U.S. Pat. No. 3,870,481 is incorporated by reference herein.
U.S. Pat. No. 3,870,481 discloses and claims a process for producing synthetic natural gas from crude oil which encompasses vaporizing a substantial portion of the crude oil at a temperature of between 600.degree. and 1,000.degree. F., thereafter introducing the vaporized crude oil and hydrogen gas into a gasification vessel maintained at a temperature in excess of 1,000.degree. F. wherein the feedstream is gasified producing an effluent consisting essentially of hydrogen, hydrogen sulfide, methane, ethane and residual aromatic hydrocarbons; thereafter cooling the effluent gas stream to ambient temperature and recovering the waste heat, drying the effluent and removing the hydrogen sulfide and residual aromatics from the effluent, cryogenically separating the methane and the ethane from the hydrogen and thereafter reacting the ethane with steam to produce additional methane and carbon dioxide and removing the carbon dioxide from the stream. The two methane streams are combined and discharged into a product pipeline or storage vessel.